Increasing the sensitivity of an amperometric, YSZ-based total-NOx sensor by opening the gas diffusion pathways in a porous La0.8Sr0.2MnO3 electrode

To boost the sensitivity of amperometric total-NO_x sensors, polymethyl methacrylate (PMMA) was employed as a pore former to open up the diffusion pathways of a porous La_0.8Sr_0.2MnO₃ (LSM) sensing electrode (SE). The porous LSM was characterized through scanning electron microscopy and mercury intrusion porosimetry, and its sensing performance was evaluated in a test setup based on a dynamic gas mixer. The results indicate that adding PMMA increases the gas diffusion pathway and the porosity of SE. Specifically, the NO_x sensitivity increased from 4.794 to 6.516 μA/decade, then decreased to 2.428 μA/decade, with the increase in the SE porosity. These results suggest that high SE porosity benefits gas diffusion but diminishes the three-phase boundary for electrochemical reactions. Meanwhile, the sensor exhibited remarkable selectivity and consistency, which means that opening the gas diffusion pathway using PMMA is a reliable technology for high-temperature NO_x sensors.